Back hoe



y 13, 1969 R. .1. BUTTRAM 3,443,705

BACK HOE Filed Aug. 9, 1967 All 3. 1

is n H 22 Fl 9 2 EXTEND 7 ROTATE INVENTOR. ROBERT J. BUTTRAM United States Patent 3,443,705 BACK HOE Robert J. Buttram, Terre Haute, Ind., assignor of one-half to Paul O. Her-twig, Terre Haute, Ind. Filed Aug. 9, 1967, Ser. No. 659,390 Int. Cl. E021? 3/74, 3/84; G09f 9/00 U.S. Cl. 214-138 6 Claims ABSTRACT OF THE DISCLOSURE A back hoe including a boom, a crowd arm pivoted to the distal end of the boom, and a bucket pivoted to the distal end of the crowd arm. A pair of piston cylinders are pivotally mounted on the boom and can have their pistons projected a desired distance to prevent digging of the back hoe below a desired depth by engaging a pair of abutments mounted on the crowd arm.

BACKGROUND OF THE INVENTION Field of the invention.This invention relates to earthworking apparatus and more particularly to a back hoe.

Description of the prior art.-The conventional back hoe intended for digging trenches and the like includes a boom, a crowd arm and a bucket. In operation the boom is usually set at a fixed angle and the crowd arm and bucket are used to scoop out the earth to dig the trench. The operator of the back hoe must rely upon his expertise to dig the trench to the proper depth inasmuch as marking stakes and the like frequently are not of too much assistance in guiding the operator. The various prior art devices as disclosed, for example, in the U.S. Patents 2,484,709 to Heath, 2,669,367 to Wills et al., 3,073,465 to Strnad and 3,220,578 to Pilch either provide no solution to this problem or do not provide an entirely satisfactory solution.

SUMMARY OF THE INVENTION One embodiment of this invention might include in a back hoe, a boom, a crowd arm pivoted to said boom, means for pivoting said crowd arm relative to said boom, a pair of abutments mounted on said crowd arm, a pair of piston cylinders mounted on said boom, means for projecting the pistons of said cylinder to positions where they can engage said abutments to limit the pivoting of said crowd arm relative to said boom, and means for changing the angle of mounting of the cylinder on said boom to locate the distal ends of said piston for engagement with said abutments.

One object of this invention is to providean improved back hoe.

Another object of this invention is to provide a back hoe which includes an automatic limiting device preventing digging below any desired depth.

Related objects and advantages will appear as the description proceeds.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevation of a back hoe embodying the present invention.

FIG, 2 is a fragmentary enlarged top plan view of a portion of the structure of FIG. 1.

FIG. 3 is a front elevation of indicating apparatus for the back hoe.

FIG. 4 is a fragmentary side elevation of an alternative embodiment of the present invention.

FIG. 5 is a hydraulic schematic diagram of the appara tus of FIGS. l-3 and FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawing and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

Referring now more particularly to the drawing, there is illustrated a back hoe apparatus which includes a vehicle 10 adapted to move around on wheels 11. Pivotally mounted upon the vehicle 10 is a boom 12. The boom may be swung to various positions by means of a piston cylinder 15 which is connected by its piston 16 to the boom and by its cylinder 17 to the vehicle 10.

The distal end 20 of the boom has swingably mounted thereon a crowd arm 21 which has mounted at its distal end 22 a bucket 25. The norm-a1 digging operation of the back hoe apparatus is to set the "boom 12 at a desired angle of perhaps 15 or and to perform the digging operation with the crowd arm 21 and the bucket 25. When the operator is so operating the back hoe, it is possible for him to dig too deeply in the earth 26 by permitting the angle which the crowd arm 21 forms with the boom 12 to become too acute. Of course, the increasing and decreasing of the angle between the boom 12 and the crowd arm 21 is carried out by a piston cylinder 27 which is connected between the boom 12 and the crowd arm 21 while the pivoting of the bucket 25 on the crowd arm 21 is carried out by the piston cylinder 30.

Pivotally mounted upon the crowd arm 21 are abutments 31. The abutments 31 are weighted so that the abutment surfaces 32 always assume a generally perpendicular or slightly upwardly facing angle. The abutments 31 should be capable of swinging to a position wherein the abutment surfaces 32 are parallel to the pads 35 mounted on the distal ends of the pistons 36. Each of the abutments 31 is pivoted to the crowd arm 21 by a rod or pin 37 and the center of gravity of the abutments 31 is spaced from the axis of the pin 37 in a direction below the pin as the abutments are viewed in FIGURES 1 and 4.

A pair of hydraulic cylinders 40 are pivotally mounted on the boom 12 and are adjusted as to angular position about the pivotal axis 41 by means of a rotary air motor 42 which is connected to the shaft 45 upon which the piston cylinders 40 are mounted through a spur gear arrangement including the gears 46, 47, 48 and 49. It

can be seen that each of the gears in the gear train are larger so that the motion of the air motor 42 is substantially stepped down at each piston 40. The spur gears 47 and 48 are mounted upon a shaft 50 which is rotatably mounted on the boom 12. The spur gears 49 are aflixed to a shaft 45 which is also rotatably mounted on the boom 12.

The amount of extension of the piston 36 of each cylinder 40 is sensed and read in the cab 51 of the vehicle 10 by means of a rack 52 which drives a worm wheel 55 coupled to a gear box 56. The amount of movement of the rack 52 is substantially stepped down by the gear box or transmission 56 until this movement is represented by a lever 57 which moves through a relatively small angle. A sheathed cable 60 has its sheath fixed to the housing of the gear box 56 by a bracket 61 and has-its cable 62 fixed to the lever 57. The other end 65 of the sheath of the cable 60 is fixed to the dashboard 66 in the cab while the other end 67 of the sheathed cable 60 is fixed to a lever 70 having gear teeth 71 meshing with the gear teeth of a spur gear 72 fixed to a shaft 75 upon which the indicator 76 is mounted. It can be appreciated that the indicator 76 will indicate the various calibrations 77, depending, of course, upon the amount of extension of the pistons 36. The amount of rotation of the shaft 45 and the piston cylinders 40 which are mounted on the shaft is indicated by the pointer 80 which is mounted on a shaft 8.1 fixed to the spur gear 82. The spur gear 82 meshes with a gear 85 on a lever 86 which is positioned by the cable 87 of a sheathed cable 88. The other end 90 of the cable 87 is fixed to a lever 91 fixed to the shaft 45 while the sheath 92 of the cable 88 is fixed to a bracket 95 fixed to the boom 12.

It should be understood that whenever the pistons 36 of the piston cylinders 40 are projected to a certain distance, they should also be rotated to a corresponding angular position so that they will be properly located and more particularly so that their pads 35 will be properly located to engage the abutments 31 when the crowd arm moves toward the boom 12. Thus, the operator may have a chart in the cab 51 mounted along side the dashboard 66 to indicate the corresponding positions of exten sion and rotation of the piston cylinder.

Referring to FIG. 4, the amount of rotation of the piston cylinder is controlled automatically by a link 101 which is pivoted at 102 at the same axis as the pivotal connection of the boom 105 and the crowd arm 106. Also, preferably the abutment is mounted on the crowd arm 106 for pivoting about an axis which coincides with the axis of pivotal connection of link 101 and piston 111 when the apparatus is in the position of FIG. 4. By such an arrangement, the pad 107 is always properly located for engagement with the abutment 110 no matter what the amount of extension of the piston 111. In other words, as the piston 111 is projected and retracted, the piston cylinder 100 automatically changes its angle and rotates about the pivotal axis 1.12 upon which the piston cylinder 100 is mounted on the boom 105. In other respects, the embodiment of FIG. 4 operates similarly or identically to the back hoe of FIGS. 1, 2 and 3. Of course, it is'not necessary to have two of the dials as illustrated in FIG. 3 since only the amount of extension of the piston is necessary in order to control the device from the cab 51.

Referring to FIG. 5, there is illustrated one of the pistons 40 which, by the way, may have their piston rods 36 fixed relative to one another so that they always project the same distance. The piston 40 has associated therewith a hydraulic pump 200 which has an output 201 and an input 202. The pump 200 draws hydraulic fluid from a sump 205. The input to the sump 205 is through line 206. Coupled across the lines 201 and 206 is a pressure valve 207 which permits passage of fluid when the pressure differential between the lines 201 and 206 becomes too great. The valve 210 is controlled in .4 the cab 51 and has three positions. In one position, the fluid within the lines 211 and 212 is blocked in those lines and cannot flow through the valve 210. In another position of the valve 2.10, the line 212 is connected to the line 201 so that the output of the pump 200 is pumped into the inlet 215 of the piston cylinder 40. In this same second position of the valve 210, the line 211 is connected to the line 206 so that as hydraulic fluid is pumped into the line 212, causing the piston 36 to move rightwardly, the other side of the piston forces fluid out through the line 211 and through the line 206 into the sump 205.

The third position of the valve 210 is reverse to the second position and connects the line 201 to the line 211 and also connects the line 206 to the line 212. Of course, in this position, the piston is caused to project by the hydraulic fluid in the cylinder 40. It can be appreciated that the three positions of the valve 210 make possible projecting and retracting the piston 36 and also make possible blocking or locking of the piston 36 in any desired amount of projection.

In operation, the calibrations 77 are so set up as to indicate the depth limitations that the various amounts of projection of the pistons 36 represent. Of course, there may be three sets of calibrations on the extend portion of the dashboard 66, which three sets correspond to perhaps three positions of the boom 12. When the pistons 36 of the cylinders 40 are projected to the position indicated on the extend portion of the dashboard which correspond to the depth limitation desired by the operator, the operator merely operates the back hoe in conventional fashion. Whenever the crowd arm 21 begins to move past the position at which the depth of the trench would be too great, the pistons 36 engage the abutments 31 preventing the bucket 25 from digging too deeply.

It will be evident from the above description that the present invention provides an improved back hoe. It will also be evident from the above description that this invention provides a back hoe which includes an automatic limiting device preventing digging below any desired depth.

I claim:

1. In a back hoe, a boom element, a crowd arm element pivoted to said boom, means for pivoting said crowd arm relative to said boom, and adjustable means between the crowd arm and boom for limiting the amount of pivoting of said crowd arm toward said boom and regulating the depth of cut of said crowd arm.

2. In a back hoe, a boom element, a crowd arm element pivoted to said boom, means for pivoting said crowd arm relative to said boom, and adjustable means for limiting the amount of pivoting of said crowd arm toward said boom, said adjustable means comprising an abutment mounted on one of said elements, a piston cylinder mounted on the other of said elements, means for projecting the piston of said cylinder to a position where it can engage said abutment to limit the pivoting of said crowd arm relative to said boom, and means for changing the angle of mounting of the cylinder on said boom to loment to locate the distal end of said piston for engagement with said abutment.

3. The back hoe of claim 1 wherein said adjustable means comprises an abutment mounted on said crowd arm, a piston cylinder mounted on said boom, means for projecting the piston of said cylinder to a position where it can engage said abutment to limit the pivoting of said crowd are relative to said boom, and means for changing the angle of mounting of the cylinder on said boom to locate the distal end of said piston for engagement with said abutment.

4. The back hoe of claim 3 wherein the means for projecting said piston comprises a hydraulic pump arrangement, said means for changing the angle of mounting of said cylinder comprising a rotary air motor, said piston cylinder being mounted pivotally on said boom, and gear means coupling said piston and air motor.

5 6 5. The back hoe of claim 3 wherein said means for References Cited changing the angle of mounting of said cylinder com- UNITED STATES PATENTS prises a link pivoted at one end to the distal end of said piston and pivoted at its other end to the pivotal con- E fi 1 mi igi nection of said boom and crowd arm, said piston cylinder 5 1503813 8/1924 Burke 214 138 being mounted pivotally on said boom.

6. The back hoe of claim 4 additionally comprising an HUGO O. SCHULZ, Primary E i indicator for indicating the angular position of said cylinder, and an indicator for indicating the distance that said piston is projected. 116-124; 214761 

